Leaf Shutter
This is how Camerapedia.org defines a leaf shutter:
A leaf shutter is made of a series of overlapping metal blades arranged in a circular pattern, usually positioned near the iris within a lens. The blades are attached to a rotating ring by pins at their ends, and are opened and closed by turning the ring. Various spring and clockwork mechanisms in the shutter are used to control the delay between opening and closing the blades, and hence the exposure time.
They go on — but here is a description given to me of the shutter sequence, by a camera specialist I asked, specifically about the Mamiya-Sekor 528TL.
For viewing, the shutter is fully open, mirror is down and film gate flap covers the film aperture. Upon releasing the exposure button, the mirror rises, the shutter closes, and the rear flap clears the film gate. The shutter then opens and closes according to the shutter speed set. Also, the lens diaphragm stops down to the set aperture. This camera instantly resets the mirror, flap, opens the shutter and the lens after every exposure.
Wow! That's a lot! That explains the musical sequence of sounds that I loved so about this camera. I think the last series of sounds, the instant resetting of the mirror, the flap, and the opening of the shutter produces a distinct sound that seems memorable to me, listening to it today.